Gear change mechanism

ABSTRACT

A gear change mechanism for a multi ratio gearbox includes selector bars movable axially one at a time to effect engagement of a particular ratio of the gearbox, each bar having a groove with which can co-operate a plurality of balls to prevent movement of two of the bars from the neutral position when the other bar is in a ratio selecting position. There is also provided a spring loaded locking member movable between a pair of balls and which when operative arrests movement of the bars at the neutral positions.

United States Patent [191 Seilly Mar. 5, 1974 [54] GEAR CHANGE MECHANISM293L237 4/1960 Backus 74/335 3,040,60l 6/1972 Lewis [75] lnvemor- Harrysally North wembley 3,076,349 2/1963 Williams ct al. 74 335 x EnglandAssignee? Limited Birmingham, Primary ExaminerArthur T. McKeon EnglandAttorney, Agent, or FirmH0lman & Stem 22 Filed: May 12, 1972 21] Appl.No.2 252,741 ABSTRACT A gear change mechanism for a multi ratio gearbox[30] Foreign Application Priority Data includes selector bars movableaxially one at a time to May 1 4 1971 Great Britain n 1 5036/71 effectengagement of a particular ratio of the gearbox, each bar having agroove with which can co-operate a 52 us. CI. 74/335 74/477 plurality ofhehe Preeht movement of of the 51 Im. Cl men 5/06 065 5/06 hem the hemePeshie" when the other is [58} Field of Search 74/335 477 a who eeleehhgPeehieh- There is Pm"idecl e I spring loaded locking member movablebetween a pair [56] References cited of balls and which when operativearrests movement UNITED STATES PATENTS of the bars at the neutralpositions.

2,847,871 8/1958 Schick 74/477 11 Claims, 3 Drawing Figures PATENTED MAR5l974 SHEET 2 0F 3 1 GEAR CHANGE MECHANISM This invention relates togear change mechanism for a multi ratio gearbox and of the kindcomprising a selector bar movable in opposite directions from a neutralposition, the bar being connected to gear selector members whereby whenthe bar is moved in one direction from its neutral position one gearratio of thegearbox will be selected and when moved in the oppositedirection from its neutral position another gear ratio of the gearboxwill be selected, the gearbox when the bar is in the neutral positionbeing in the neutral condition.

The object of the invention is to provide a gear change mechanism foruse on such a gearbox.

According to the invention a gear change mechanism for a gear box of thekind specified comprises power operated actuating means operativelyconnected to said selector bar to effect movement thereof, said poweroperated actuating means being reversible whereby the bar can be movedin opposite directions, and locking mechanism operable to halt themovement of the bar atthe neutral position. I

In the accompanying drawings:

FIG. 1 is a sectional side elevation through a portion of a gear changemechanism;

FIG. 2 is a sectional side elevation through another portion of themechanism, and

FIG. 3 is a part sectional plan view of the portion of the mechanism ofFIG. 1.

One example of a gear change mechanism will now be described withreference to a mechanism for selecting the gears of a multi-speedgearbox having five for ward gears and a reverse gear. The gearbox isofa conventional form having where appropriate, synchronising devicesand the selection of each ratio is carried out by movement in one or theother direction of one of three selector bars. The bars are shown at 10,11 and 12 in FIG. 1 and in the position shown in FIG. 1 the bars areeach in the neutral position. Each bar can be moved in one or the otheraxial direction to effect selection of one of the gear ratios of thegearbox and each bar is provided or connected to selector members 9 toeffect the actual engagement of the particular ratios. A portion of thegear mechanism being shown at 8. In the position shown in FIG. 1 eachbar is in the neutral position so that none of the gear ratios of thegear box are selected.

For moving the bars in opposite directions three reversible electricmotors are provided, one such motor and part of its associated drivemechanism, being shown in FIG. 2. The motor housing is indicated at 13and the output shaft of the motor is coupled to a drive shaft 14 bymeans of a speed reduction mechanism which incorporates a peripherallytoothed wheel 15 mounted about the shaft 14 and drivingly connectedthereto through the intermediary of a clutch. The clutch comprises aplate 16 which is secured to the shaft 14 and a second plate 17 which isaxially movable thereon. The plate 17 is urged towards the plate 16 bymeans of a spring Washer 18 and the plates mount annular frictionmembers 19 which bear against the web of the gear wheel 15.

The output shaft terminates in a crank arm 20 which is provided with aball 20a of a ball and socket, the socket 20b being formed in a partmounted on the associated selector bar.

In operation, energisation of the motor will effect movement of theassociated selector bar in an axial direction, the particular directiondepending upon which way the motor armature rotates.

When the mechanism is in use, all the bars must be in the neutralposition or one bar only-may be in one of two extreme positions onopposite sides of the neutral position. It is essential therefore toensure that the motor is switched off when the appropriate position isreached and for this purpose there is provided on the motor a switchmechanism 21. The mechanism is accommodated within a housing secured, tothe motor housing and the plate 17 has secured thereto an electricallyinsulating annular member 22 which carries contacts for engagement bybrushes 23 supported in the switch housing. In addition the switchhousing carries blades for connection of the switches into externalelectric circuit means. This circuit means includes a manually operableselector switch whereby the direction of rotation of one of the threemotors can be determined so as to effect engagement of the particulargear ratio. In addition the circuit means ensures that before oneselector bar can be moved the other two selector bars are in the neutralposition.

With such an arrangement it will be appreciated that the motor and partsconnected thereto will have considerable inertia so that the arm 20 andtherefore the associated selector bar will continue to move even whenthe supply of electric circuit to the motor is removed. This does notmatter when the bars are moving towards their extreme positions however,it is of considerable importance when the bars are being moved to theirneutral position. It is possible for the inertia to carry the bar pastthe true neutral position and a locking mechanism which is shown in FIG.1 is provided to prevent over-run of the bars beyond the neutralposition.

With reference to FIG. 1 there is associated with each selector bar aspring loaded ball 24 which locates in one of three grooves 25 disposedin spaced relationship on each selector bar. The provision of such aball is of course very well known and forms no part of the presentinvention.

Each selector bar is slidably accommodated within a bore, the axes ofthe three bores extending substantially parallel to each other.Moreover, between the inner and the two outer bores, extend a pair offurther bores 26, 27 and each of these bores accommodates a pair ofballs 28. The central selector bar 11 is provided with a transverselyslidable push piece 29 positioned so that its ends can contact theadjacent balls 28 in the bores 26 and 27. I

Each selector bar is provided with grooves 30 to partly accommodate therespective balls 28 and it will be noted that the bar 11 is providedwith grooves 30 on its opposite sides. Moreover, movable between theballs 28 in the bore 26 is a tapered locking member 31 which is axiallymovable and which is spring loaded by means of a spring 32, to theposition in which it is shown, In this position and with each bar in theneutral position, the balls 28 in the bore 26 are accommodated withinthe respective grooves 30 of the bars 10 and 11. Moreover, the pushpiece 29 transmits movement to the balls 28 which are accommodated inthe bore 27, to prevent movement of the bar 12. Therefore before any oneof the bars can be moved, the locking member 31 must be moved axiallyagainst the action of the spring 32. When this occurs one only of theselector bars may be moved axially and during this movement the balls 28will move appropriately to prevent movement of the other two bars.

ln order to prevent one of the bars overshooting the neutral positionthe locking member 31 prior to movement of the bar towards the neutralposition, is allowed to move under the action of its spring to effectseparation of the balls 28 in the bore 26. In fact such separationcannot occur until all the bars are in the neutral position. As themoving bar attains the neutral position the balls 28 move appropriatelyto allow the locking member 31 to take up the position shown. Once thisposition is attained no further movement of the bar can take place sothat it is effectively halted and locked in the neutral position.

The locking member 31 is connected to a solenoid armature 33, thesolenoid having a winding 34. When the winding is energised the armature33 is moved upwardly and moves the locking member 31 against the actionof the spring 32. A certain amount of lost motion is permitted betweenthe armature and the locking member 31 to allow the armature to moverapidly. Moreover, at its extreme position the armature 33 engages aswitch actuating member 35, the switch forming part of the circuitmeans.

It will be appreciated that various modifications can be made to themechanism described above. For instance the gear reduction mechanismassociated with the motor may be replaced by some other form ofmechanism such for instance as a mechanism which provides a linearmovement upon operation of the electric motor.

1 claim:

1. A gear change mechanism comprising a selector bar movable in oppositedirections from a neutral position, the bar being connected to gearselector members of an associated gear box whereby when the bar is movedin one direction from its neutral position one gear ratio of the gearboxwill be selected and when moved in the opposite direction from itsneutral position another gear ratio of the gearbox will be selected, anelectric power operated actuating means operatively connected to saidselector bar to effect movement thereof, said power operated actuatingmeans being reversible whereby the bar can be moved in oppositedirections, and locking mechanism operable to halt the movement of thebar at the neutral position.

2. A mechanism as claimed in claim 1 in which said locking mechanismcomprises a groove on the selector bar, a locking member, a locking partmovable by said locking member into said groove on the selector bar whenthe bar reaches the neutral position, thereby to prevent furthermovement of the bar, and resilient means for loading said locking memberto move said locking part.

3. A mechanism as claimed in claim 2 including means operable to effectmovement of said spring loaded member to permit movement of the bar.

4. A mechanism as claimed in claim 3 in which said means comprises asolenoid having an armature connected to said spring loaded member.

5. A mechanism as claimed in claim 4 including means providing lostmotion between the armature and said member.

6. A mechanism as claimed in claim 5 in which said locking partcomprises a ball.

7. A mechanism as claimed in claim 6 comprising a further selector barposition in spaced side by side relationship with the first mentionedbar, said further selector bar also having a groove with which canco-operate a locking part in the form of a ball, said spring loadedlocking member being insertable between said balls to effect locking ofboth bars in the neutral position.

8. A mechanism as claimed in claim 7 including a passage extendingbetween the selector bars, said balls being located in said passage, theballs and grooves being chosen in relation to the length of the passagesuch that when one bar is moved from the neutral position the other barwill be held in the neutral position.

9. A mechanism as claimed in claim 8 including an additional bar whichis disposed parallel to but spaced from the other bars, a push memberlocated in the central one of said bars, said push member transmittingmotion between the balls intermediate the first mentioned and thefurther selector bars and further balls disposed between the additionalbar and the central one of said bars.

10. A mechanism as claimed in claim 3 in which said electric poweroperated actuating means comprises an electric motor.

11. A mechanism as claimed in claim 10 in which said motor includes areduction mechanism incorporating an overload clutch.

1. A gear change mechanism comprising a selector bar movable in oppositedirections from a neutral position, the bar being connected to gearselector members of an associated gear box whereby when the bar is movedin one direction from its neutral position one gear ratio of the gearboxwill be selected and when moved in the opposite direction from itsneutral position another gear ratio of the gearbox will be selected, anelectric power operated actuating means operatively connected to saidselector bar to effect movement thereof, said power operated actuatingmeans being reversible whereby the bar can be moved in oppositedirections, and locking mechanism operable to halt the movement of thebar at the neutral position.
 2. A mechanism as claimed in claim 1 inwhich said locking mechanism comprises a groove on the selector bar, alocking member, a locking part movable by said locking member into saidgroove on the selector bar when the bar reaches the neutral position,thereby to prevent further movement of the bar, and resilient means forloading said locking member to move said locking part.
 3. A mechanism asclaimed in claim 2 including means operable to effect movement of saidspring loaded member to permit movement of the bar.
 4. A mechanism asclaimed in claim 3 in which said means comprises a solenoid having anarmature connected to said spring loaded member.
 5. A mechanism asclaimed in claim 4 including means providing lost motion between thearmature and said member.
 6. A mechanism as claimed in claim 5 in whichsaid locking part comprises a ball.
 7. A mechanism as claimed in claim 6comprising a further selector bar position in spaced side by siderelationship with the first mentioned bar, said further selector baralso having a groove with which can co-operate a locking part in theform of a ball, said spring loaded locking member being insertablebetween said balls to effect locking of both bars in the neutralposition.
 8. A mechanism as claimed in claim 7 including a passageextending between the selector bars, said balls being located in saidpassage, the balls and grooves being chosen in relation to the length ofthe passage such that when one bar is moved from the neutral positionthe other bar will be held in the neutral position.
 9. A mechanism asclaimed in claim 8 including an additional bar which is disposedparallel to but spaced from the other bars, a push member located in thecentral one of said bars, said push member transmitting motion betweenthe balls intermediate the first mentioned and the further selector barsand further balls disposed between the additional bar and the centralone of saId bars.
 10. A mechanism as claimed in claim 3 in which saidelectric power operated actuating means comprises an electric motor. 11.A mechanism as claimed in claim 10 in which said motor includes areduction mechanism incorporating an overload clutch.